This invention relates to work locating method and apparatus and more particularly to work locating apparatus and method which include provisions for instantaneous and continuous correction of work member location errors due to expansion, contraction, or meterological effects upon the apparatus or other factors.
In U.S. Pat. No. 3,622,244, a laser interferometer is used to measure the displacement of a work member but the illustrated apparatus has no provisions for correcting work member expansion or contracting during the work operation. In some prior art patents, however, compensation or ennvironmental effects is considered.
In U.S. Pat. No. 3,520,613, provisions have been made for determining the temperature of the part being positioned and repositioning that part in accordance with temperature variation so determined and other environmental factors such as atmospheric pressure and humidity. In U.S. Pat. No. 3,477,789 temperature compensation is derived from temperature dependent means and applied to the data produced by the measuring apparatus after the data is taken. Such systems depend upon the accuracy and the operability of the temperature or other sensors utilized and are subject to limitations such as the correspondence between the linearites or nonlinearites of the sensor and the system being corrected.